docs: update stale Cavos listing on developer tools page

[adrianvrj]

Summary

The Cavos entry on the developer tools cheatsheet still points at the old Aegis product URL and describes the previous wallet-infrastructure positioning (including an overclaim of “gasless transactions”).

This PR updates only that listing to the current Cavos site and an accurate one-line description.

Before

* [Cavos](https://aegis.cavos.xyz/) is a wallet infrastructure service that enables instant wallet creation, gasless transactions, multi-provider authentication, and cross-platform SDKs

After

* [Cavos](https://cavos.xyz) is a device-native embedded self-custodial wallet SDK. Users sign in with Google or Apple; the key stays on the device and Cavos cannot move funds. Starknet, Solana, and Stellar.

• Primary link: https://cavos.xyz (docs: https://docs.cavos.xyz)
• Dropped “gasless” — gas sponsorship is pass-through, not a Cavos-provided guarantee
• No other listings changed

Test plan

• Confirm https://docs.starknet.io/learn/cheatsheets/tools Cavos bullet links to https://cavos.xyz
• Confirm neighboring dApp-tool entries are unchanged